Sensitization of Bleached Rod Photoreceptors by 11-Cis-Locked Analogues of Retinal

Photoactivation of rhodopsin initiates both excitation and adaptation in vertebrate rod photoreceptors. Bleaching of rhodopsin to free opsin and all-trans-retinal in isolated rods produces a stable desensitization (bleaching adaptation) that is much larger than expected from pigment depletion alone....

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 1990-09, Vol.87 (17), p.6823-6827
Main Authors: Corson, D. Wesley, Cornwall, M. Carter, MacNichol, Edward F., Jin, Jing, Johnson, Randy, Derguini, Fadila, Crouch, Rosalie K., Nakanishi, Koji
Format: Article
Language:English
Subjects:
Absorptance
Absorption spectra
Ambystoma
Animals
Biochemistry
Bleaching
Darkness
In Vitro Techniques
Kinetics
Larva
Light
Opsins
Pain sensitivity
photobleaching
Photons
Photoreceptor Cells - drug effects
Photoreceptor Cells - physiology
Pigments
retinal
Retinal pigments
Retinal Pigments - physiology
Retinal Pigments - radiation effects
Retinaldehyde - analogs & derivatives
Retinaldehyde - pharmacology
Retinoids - pharmacology
rods
Spectral sensitivity
Structure-Activity Relationship
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Summary:Photoactivation of rhodopsin initiates both excitation and adaptation in vertebrate rod photoreceptors. Bleaching of rhodopsin to free opsin and all-trans-retinal in isolated rods produces a stable desensitization (bleaching adaptation) that is much larger than expected from pigment depletion alone. In our experiments, a 93% bleach produced a 500-fold increase in the light intensity required for saturation of the light response. This component of adaptation was 32-fold larger than the 16-fold increase expected from pigment depletion alone. 11-cis-Retinal, when delivered to isolated rods from liposomes, combines with free opsin to form a bleachable photopigment that fully restores sensitivity. 11-cis-Locked analogues of retinal combine with opsin to form unbleachable pigments in isolated bleached rods from the tiger salamander. They restore sensitivity to a substantial (16- to 25-fold) but incomplete extent. The analogues apparently relieve a stable component of adaptation when they interact with opsin. Because these analogues do not detectably excite rods, the structural requirements of both retinal and opsin for the relief of adaptation are different from those of excitation. The biochemical basis of light adaptation resulting from pigment bleaching and the minimum structural requirements of retinal for its relief remain to be determined.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.87.17.6823